1. Field of the Invention
This invention relates to waterbed mattresses.
2. Prior Art
Since the late 1960's, when waterbeds were first introduced, waterbeds have been gaining increasing acceptance. It has been recognized that waterbeds provide dimensions of comfort and bodily support not available from conventional inner spring or foam mattress bedding systems. Waterbeds have also become favored for their therapeutic and other user qualities.
However, waterbeds have been beset with a major disadvantage. This disadvantage is the tendency for wave motion to be created in the waterbed mattress. Wave motion in the mattress can make users of the waterbed uncomfortable, and consumer fear of "seasickness" has inhibited the acceptance of waterbeds.
Heretofore, attempts have been made to provide a waterbed mattress that would retard or dampen wave motion. The June, 1979 issue of California Business, in an article by Bob Gilbert entitled "Taking the Plunge" (p.54), reports at page 60 that it was hoped "hybrid" beds would solve this wave motion problem. A hybrid bed comprises a water mattress with a foam topping placed over the mattress. Unfortunately, hybrid beds are as susceptible to wave motion as conventional waterbeds.
The same article reports, also at page 60, that attempts to achieve motionless characteristics include putting plastic baffles inside the waterbed mattress, and "floating a jell on the top half of a mattress, separated from water on the bottom half by a vinyl sheet."
Another recent attempt to reduce wave motion includes construction of baffle chambers within the mattress. The chambers' side panels are welded to the mattress' bottom sheet. The chambers' tops, connected to the upper edges of the side panels, are made of foam and allowed to float free of any contact with the mattress in an effort to form an internal breakwater.
The above discussed attempts to reduce wave motion have met with various degrees of success. Unfortunately, whatever degree of wave dampening achieved by such systems has often been more than offset by increased costs and complexities of manufacture. Moreover, such systems are often expensive to ship, and they pose difficulties to consumers who wish to empty, reposition, and refill their waterbeds. Some systems are more prone to leakage. Waterbed systems requiring special gels or additives cause additional problems and expenses. For example, special kits are needed to dissolve the gel for draining. Also, conventional heaters cannot be used with waterbed mattresses containing gels because of the poor heat transfer properties of gels. When conventional heaters are used in connection with waterbeds comprising gels, the heaters have been known to burn out and the vinyl comprising the mattress has been known to melt.
U.S. Pat. Nos. 3,702,484 and 3,736,604, issued to R. Carson, Jr., and to S. Tobonick and A. Saminoff, respectively, disclose hybrid type waterbeds.
Waterbed mattresses comprising baffles to dampen wave motion are disclosed in C. Mollura's U.S. Pat. No. 4,141,770 and I. Fogel's U.S. Pat. No. 4,152,796. Also, U.S. Pat. No. 4,192,031, issued to I. Fogel is illustrative of such waterbeds comprising baffle chambers. In Fogel '031, the foam is preferably closed cell foam and in any event is thin and serves as a float or "cork" to support the baffle chambers' top. The Fogel '031 baffle achieves wave reduction as a result of the top of the chamber wiping against the upper sheet of the waterbed. Such a waterbed is still subject to violent movement, though for a shorter time than conventional waterbeds. Because the baffle's side panels are welded, or heat sealed, to the bottom sheet of the mattress, such mattress is more susceptible to leakage.
U.S. Pat. No. 3,349,953, issued to R. Conaway and J. Spindler discloses a tank with a baffle system inserted to prevent sloshing of liquid in the tank.
U.S. Pat. No. 3,748,669, issued to F. Warner, discloses a waterbed mattress comprising fluid impervious cells distributed throughout the mattress to displace liquid which would otherwise be required to fill the mattress, thus, reducing the total weight of the mattress. German Offenlegungsschrift No. 2,431,431, issued to Mr. Schmidt shows a similar waterbed mattress. U.S. Pat. No. 3,787,908, issued to W. Beck and N. Sweeny, also discloses a liquid filled mattress having low density cellular particles suspended throughout the liquid in order to reduce the weight of the filled mattress. The cellular particles also improve the insulative properties of the liquid fill. Beck et al. also teach adding a viscosity modifier to the liquid fill to improve the waterbed mattress's dimensional stability characteristics.
U.S. Pat. No. 3,585,356,issued to C. Hall, discloses producing a dampening effect by placing a suitable solid material in suspension in the fluid within the mattress. Hall teaches that ground or shredded Styrofoam at a volume ratio of about one to three to water produces a dampening effect. Hall also teaches replacing the Styrofoam by starch or other material which will stay in suspension in the fluid. An alternative embodiment is also shown by Hall, wherein small blocks of a material such as styrofoam float upon the entire surface of the fluid. Hall teaches that the blocks rub against each other and their reaction with the fluid provides independent support for all parts of a body positioned on the waterbed mattress.
D. McGrew, in U.S. Pat. No. 3,810,265, teaches dampening wave motion by adding a water soluble viscosity increasing agent to the liquid fill of the mattress. McGrew also discusses the preference that the water mattress not be secured to the frame, especially along the upper marginal surface of the mattress to insure preservation of even bouyancy and prevention of a shear-producing hammocking effect. For this purpose the upper surface of the mattress may carry some slack as provided by a plurality of pleats in the upper mattress surface. Additionally, a foam rubber or other elastic pad may be floatably positioned on the upper outside mattress surface for added comfort or temperature compensation.
U.S. Pat. No. 3,574,873, issued to J. Weinstein, discloses a cushion for preventing the formation of decubitus ulcers. The cushion comprises a flexible and elastic envelope surrounding and enclosing an internal matrix formed of open cell foam material. The internal matrix occupies the entire depth of the envelope. At suitable places the upper surface of the envelope is bonded to the top surfaces of the foam matrix. The envelope also encloses a fluid which passes through the open cells of the foam. This fluid is usually air, although water may be used in addition to air to help dissipate heat in the cushion. Weinstein teaches filling the 2/3 of the cushion's volume with water and to have the remaining 1/3 as air at atmospheric pressure. Weinstein also teaches filling the cushion completely with water. However, since the matrix is relatively inelastic, a stiffer cushion results when it is filled completely with water. At no time is Weinstein concerned with the formation of waves in his cushions as the cushion does not contain enough water for waves to become a factor.
The systems described by the above discussed patents have not achieved a satisfactory wave dampening effect without compromising the qualities expected of conventional waterbeds. Moreover, such systems bear the disadvantages discussed earlier; namely, increased costs and complexities of manufacture, increased costs of shipping, increased difficulties in emptying and refilling, greater likelihood of leakage, and increased maintenance costs.